MOST children in Newtown have returned to school for the first time as the toll of funerals for the 26 dead continues on a grey, wet day.

The debate on gun control in the US sharpened as President Barack Obama threw his weight behind a bill to reintroduce a ban on civilians owning assault weapons and a prominent investor said it would sell shares in the company that makes the rifle thought to be used in Friday's shooting.

White House spokesman Jay Carney said the president would support a law proposed by Democratic Senator Dianne Feinstein to prohibit the arms, defined as certain types of semi-automatic firearm with removable magazines.

"He is actively supportive of, for example, Senator Feinstein's stated intent to revive a piece of legislation that would reinstate the assault weapons ban," Mr Carney said, when asked what Mr Obama would do about gun control.

Mr Carney said Mr Obama would also support any move to ban high-capacity clips - magazines that hold dozens of rounds - and close the so-called "gun show loophole" that allows unlicensed individuals to sell guns privately.

And there were more funerals planned for the 20 young students - including for six-year-olds Jessica Rekos and James Mattioli - as well as several wakes, including one for teacher Victoria Soto, who has been praised as a hero for sacrificing herself to save several students in one of the worst mass shootings in US history.

The two funerals on Monday ushered in what will be a week of memorial services and burials for the 20 children and six adults massacred at Sandy Hook Elementary School in Connecticut. Deborah Lutterbeck reports.

Private equity firm Cerberus Capital Management announced it would sell its stake in major arms manufacturer Freedom Group, saying in a statement, "It is apparent that the Sandy Hook tragedy was a watershed event that has raised the national debate on gun control to an unprecedented level."

A school bus passes a makeshift memorial to the victims of the Sandy Hook Elementary School shooting as it takes students to Newtown High School. Picture: AFP

He shouted "Let me in, let me in!" said Nicholas, who was interviewed with his parents Jose and Sherry.

When the first shots rang out at Sandy Hook Elementary School on Friday, music teacher Maryrose Kristopik ushered Nicholas's class into a large closet and quickly locked the door.

"We held onto the instruments to not make any noise," said Nicholas, who clutched a gong.

"We were all really scared and then we prayed... Miss Kristopik gave us all lollipops. We thought it would be our last snack.

And the mystery of why a smart but severely withdrawn 20-year-old, Adam Lanza, shot his mother to death in bed before rampaging through Sandy Hook Elementary, killing 20 children ages six and seven, was as deep as ever.

The first two children, including the youngest victim, were buried on Monday, the first of a long, almost unbearable procession of funerals as the rest of the country prepared for the Christmas holidays.

Six-year-olds James Mattioli (left) Olivia Engel (right) were killed in the Newtown shooting.

Classes resumed on Tuesday for Newtown schools except those at Sandy Hook, where the school will remain closed indefinitely.

"It's the right thing to do. You have to send your kids back. But at the same time I'm worried," said Dan Capodicci, whose 10-year-old daughter attends another local school. "We need to get back to normal.

Classes began with up to two hours delay and extra security was posted outside buildings, with a squad car at Newtown Middle School and lines of yellow police tape keeping away journalists at Saint Rose Elementary.

At Hawley Elementary School, a couple accompanying their young son held hands and hugged the policeman at the entrance.

"He was very happy to get back with his friends," one mother said, declining to give her name. But the father said he could not describe his emotions on what should have been an ordinary school run.

Police are positioned outside the home of Nancy Lanza, who was killed by her son Adam before going on his rampage. Picture: AFP

Investigators say Lanza had no ties to the school he attacked, and they have found no letters or diaries that could explain why he targeted it. He forced into the school shortly after its front door locked as part of a new security measure. He wore all black and is believed to have used a Bushmaster AR-15-style rifle, a civilian version of the military's M-16. Versions of the AR-15 were outlawed in the US under the 1994 assault weapons ban, but the law expired in 2004.

Debora Seifert, a spokeswoman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said both Lanza and his mother fired at shooting ranges and visited ranges together.

New York City's billionaire Mayor Michael Bloomberg, perhaps the most outspoken advocate for gun control in US politics, again pressed Obama and Congress to toughen gun laws and tighten enforcement.

Pallbearers carry the casket containing the body of James Mattioli into St Rose of Lima Roman Catholic Church for funeral services. Picture: AP

"If this doesn't do it," he asked, "what is going to?"

At least one senator, Virginia Democrat Mark Warner, said on Monday that the attack has led him to rethink his opposition to the ban on assault weapons. And West Virginia Senator Joe Manchin, a Democrat who is an avid hunter and lifelong member of the powerful National Rifle Association, said it's time to move beyond the political rhetoric and begin an honest discussion about reasonable restrictions on guns.

In Newtown on Monday, minds were on mourning.

Two funeral homes filled for Jack Pinto and the youngest victim, Noah Pozner, who turned six just two weeks ago.

A rabbi presided at Noah's service, and in keeping with Jewish tradition, the boy was laid to rest in a simple brown wooden casket with a Star of David on it.

A woman comforts a boy as mourners depart Honan Funeral Home after the funeral for six-year-old Jack Pinto in Newtown, Connecticut.

"I will miss your perpetual smile, the twinkle in your dark blue eyes, framed by eyelashes that would be the envy of any lady in this room," Noah's mother, Veronique Pozner, said at the service, according to remarks the family provided to The Associated Press. Both services were closed to the news media.

Noah's twin, Arielle, who was assigned to a different classroom, survived the killing frenzy.

At six-year-old Jack Pinto's Christian service, hymns rang out from inside the funeral home, where the boy lay in an open casket.

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